Rotary lawn mowers are known which comprise a wheeled housing, a rigid cutting blade rotatable in a cutting chamber in the housing, and a generally U-shaped handle extending upwardly and rearwardly from the housing for allowing an operator to guide and manipulate the mower. Many mowers of this type, as well as many other outdoor power equipment units, have a self propel drive system that propels the mower at a variable ground speed controlled by the operator. Typically, a pivotal ground speed control bail is provided on the handle of the mower. The bail can be pivoted from an open position towards a closed position with the degree of closure determining the ground speed of the mower.
Such pivotal bails to control ground speed are widely used. However, different mowers have bails that pivot in different ways with some pivoting from the top down and some from the bottom up. The operator must learn how to properly move and control the bail provided on the particular mower being operated. Moreover, to slow down a mower's ground speed, the operator must let up on the bail and let it return towards its open position. Since most operators tend to grip the handle tightly, and tend to keep the bail gripped in its closed position, letting up on just the bail to slow the mower down is not a natural action and must be learned.
At least one ground speed control system for an outdoor power equipment unit has been proposed which relies on pivotal motion of a portion of the handle, thereby doing away with the need for a separate pivotal control bail. In U.S. Pat. No. 4,835,949 to Seyerle, which is assigned to The Toro Company, the assignee of this invention, the top portion of the handle is pivotably connected to a lower portion of the handle. The operator pushes forwardly on the top portion of the handle as the operator grips the cross bar of the handle to increase the ground speed and pulls back on the top portion of the handle to decrease the mower ground speed.
While the Seyerle pivotal handle approach avoids the need for a separate pivotal control bail, it is still somewhat unnatural to use. Since the operator naturally pushes forwardly on the handle when directing the mower, this push would quickly move the pivotal portion of the handle to its forwardmost position where the ground speed is greatest. It is difficult to learn to pivot the handle just enough to reach a desired lower speed. Thus, the ground speed of a mower having this type of pivotal handle control system is very sensitive to the pivotal motion of the handle, making the mower jerky in use with the operator pushing forward or pulling back on the pivotal handle portion trying to find the right ground speed.